1. Field of the Invention
The present invention relates to orthopaedic cutting tools, and, more particularly, to acetabular reamers.
2. Description of the Related Art
Minimally invasive surgical techniques have the advantage of reducing the trauma to tissue surrounding the surgical site during a surgical procedure. The small incision that surgeons are using for minimally invasive hip surgery make it difficult to insert a current full size hemispherical acetabular reamer through the small incision. However, the full size hemispherical acetabular reamer cuts a full hemispherical shape in the acetabulum with minimal wobbling and therefore provides an excellent preparation for the hip joint prosthesis. Additionally, a reamer is required to be connected to a driver, which is in turn connected to a rotational tool. The driver has a specific structure at the proximal (to the surgical site) end thereof, which is compatible with specific attachment mechanisms on the reamers. The drivers represent an investment on the part of the medical institution where the surgery is performed, and if the reamer is modified to be more compatible with minimally invasive surgical techniques, the driver attachment mechanism may be correspondingly modified, which necessitates the purchase of both the driver and the reamer for the medical institution. The purchase of a driver adds cost to the acquisition of the new reamer technology.
Orthopaedic reamers are known that cut off opposing segments of the hemispherical shell of the reamer. The resulting reamer, while having a reduced profile in a certain orientation, is no longer rotationally symmetric. The lack of rotational symmetry can cause vibration and wobbling of the reamer when in use. Such a cut-down reamer design can cut an irregular cavity in the acetabulum, for example, during hip joint replacement surgery. An irregular cavity in the acetabulum can reduce the expected lifetime of the hip joint prosthesis, cause discomfort for the patient and increase the wear in the artificial joint, among other problems. Additionally, a purpose of the hemispherical shell is that it provides a debris retaining cavity for cut material, thereby minimizing the surgical site contamination with the cut material from the acetabulum. By simply cutting off the sides of the reamer, such a reamer no longer provides a debris retaining cavity. Further, these reamers lose rigidity, which reduces the cutting performance of the reamer, and the reliability. Yet further, these reamers are relatively difficult to manufacture.
An acetabular reamer is known in which the shape of the reamer is modified in that one or more sides of the reamer are removed, and replaced with flat side surfaces which maintain the closed nature of the interior cavity. However, such a reamer creates stress points at the juncture of flat surfaces and the curved shell which can lead to cracks and failure of the reamer. Further, such a reamer is relatively difficult to manufacture.
What is needed in the art is an acetabular reamer with a reduced profile which includes a debris retaining capability, which cuts well, and which is relatively easy and cost effective to manufacture.